There have been other non-interruptible systems developed, which use either a separate battery or capacitor to operate the system while the batteries are being changed. These systems work, they are either awkward or somewhat limited in use for use with high current draw systems.
The most common non-interruptible battery exchange system in use today uses a high capacity capacitor which when charged will operate the system for the time it takes to change the battery. The problem is that these capacitors have limited storage capability, and therefore are limited in use with high draw system. Items such as computers (laptops) usually go into a sleep mode when this function is used to minimize the current draw.
Another technique is to use a secondary battery to perform the function of the capacitor. This is more functional for high current draw applications, and can take several variations. One approach is to us a separate battery pack, which is temporally plugged into the system while the batteries are exchanged. This is awkward since it is necessary to have usually specially designed battery pack available to accomplish the interchange. In systems which have a separate battery packs it is also common to supply two input jacks so that packs can be interchanged without interruption.
Another common battery system uses a rechargeable battery, which is maintained internal to the system. This is usually lower in capacity than the main battery. The system maintains charge on the battery, which is capable of running the system for a short period of time while the main battery is changed. When the charged battery is inserted some of the current is used to recharge and maintain this secondary internal battery.